exe0701_2.m

Matlab程序为清华大学胡广书版信号处理的上机习题答案

%---------------------------------------------------------------
% exa0701_1
%---------------------------------------------------------------
clear all;

N=28;
b1=fir1(N,0.25,boxcar(N+1));  %用矩形窗作为冲激响应的窗函数
b2=fir1(N,0.25,hamming(N+1)); %用Hamming窗作为冲激响应的窗函数
%
M=128;
h1=freqz(b1,1,M);
h2=freqz(b2,1,M);
% 分别求两个滤波器的频率响应；
t=0:1:N;
f=0:1/M:1-1/M;
M1=M/4;
for k=1:M1
   hd(k)=1;
   hd(k+M1)=0;
   hd(k+2*M1)=0;
   hd(k+3*M1)=0;
end
figure(1);
subplot(121);
plot(f,abs(h1),'r-',f,abs(h2),'g-',f,hd,'-');grid;
ylabel('abs(H)')
xlabel('omg/2pi');

hp1=unwrap(angle(h1));
hp2=unwrap(angle(h2));
hpd=zeros(1,M);
subplot(122);
plot(f,hp1,'r-',f,hp2,'g-',f,hpd,'-');grid;
ylabel('phase');
xlabel('omg/2pi');


%plot(t,zeros(1,N+1));grid;
%plot(f,abs(h1),'r-',f,abs(h2),'g-',f,hd,'-');grid;